Prior to the present invention, the general method for making silicone-styrene block polymers, as shown by J. Saam et al, U.S. Pat. No. 3,678,125, incorporated herein by reference, involved the preparation of a block of polystyrene having terminal organometallic functional groups resulting from anionic polymerization. Silicone blocks were then grown off the ends of the vinyl polymer by means of anionic ring opening of a cyclic siloxane such as hexamethylcyclotrisiloxane. The resulting ABA silicone-organic-silicone block polymer was then coupled to give a multiple sequence block polymer having good mechanical properties.
In my copending application, Ser. No. 840,168, filed Mar. 17, 1986, and assigned to the same assignee as the present invention and incorporated herein by reference, certain silicone-organic block polymers are shown which can be used as resists, impact modifiers, packaging, biomedical protheses and the like. These silicone-organic block copolymers can be made by effecting in the presence of an organic solvent, the free radical polymerization of a free radical polymerizable organic monomer and a silicone prepolymer having in its backbone or in the terminal position, at least one chemically combined bissilylpinacolate radical capable of forming a free radical-initiator upon thermolysis.
The present invention is based on my discovery that certain silicone-polyvinylarylene block copolymers which can be made by the aforementioned method of Saam et al, can be used as positive or negative resists. These silicone-polyvinylarylene block copolymers are shown by the formulas EQU --A--B--.sub.x ( 1) EQU A--B--A (2)
where A is a silicone block joined to B by carbon-silicon linkages and consists essentially of chemically combined diorganosiloxy units of the formula EQU (R).sub.2 SiO-- (3)
R is selected from monovalent C.sub.(1-14) hydrocarbon radicals and C.sub.(1-14) hydrocarbon radicals substituted with radicals neutral during anionic or free radical polymerization and B is a vinylarylene block consisting essentially of chemically combined vinylarylene units substituted with at least one acid labile group of the formula EQU OZ (4)
where Z is a tertiary organo or organosilicon radical as defined hereinafter and x is a positive integer.
The present invention is based further on my discovery that if a free radical polymerizable vinyl monomer having the formula, ##STR1## where Q is a monovalent radical selected from, --CO.sub.2 --Y, --R.sup.3 CO.sub.2 Y, and R.sup.3 OZ,
Z is as previously defined, and Y is an acid labile group as defined hereinafter, is polymerized in the presence of the silicone prepolymer of the above-mentioned Ser. No. 840,168, having at least one chemically combined bis-silylpinacolate radical, that the resulting silicone-organic block polymer also can be used as a positive or negative resist. I have further found that resist compositions sensitive to deep UV radiation in the range of from 220 to 320 nm can be made by combining the silicone-polystyrene block copolymers of Formulas (1) or (2), or the silicone-organic block polymers made by the method of Ser. No. 840,168, with an effective amount of an aryl onium salt as defined hereinafter to produce a resist composition. These resist compositions also exhibit valuable etch resistance to RIE, oxygen reactive ion etching. R.sup.1 in Formula (5) is selected from hydrogen, a C.sub.(1-8) alkyl radical or a mixture thereof, R.sup.2 is a C.sub.(1-14) monovalent hydrocarbon or a C.sub.(1-14) hydrocarbon radical substituted with radicals neutral during polymerization, and R.sup.3 is selected from C.sub.(6-14) aromatic hydrocarbon radicals and C.sub.(6-14) aromatic hydrocarbon radicals substituted with up to five nuclear bound radicals which can be the same or different and which are neutral during polymerization.